kitchen: emit valid JSON for SET_BUILD_PROPERTY annotations

client/cmd/kitchen/cook.go

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package main
 
 import (
         "encoding/json"
         "fmt"
         "io/ioutil"
@@ skipping 164 matching lines @@
         annotate("SEED_STEP", BootstrapStepName)
         annotate("STEP_CURSOR", BootstrapStepName)
         annotate("STEP_STARTED")
         props, err := parseProperties(c.Properties, c.PropertiesFile)
         if err != nil {
                 fmt.Fprintln(os.Stderr, err)
                 return 1
         }
         for k, v := range props {
                 // Order is not stable, but that is okay.
-                annotate("SET_BUILD_PROPERTY", k, fmt.Sprintf("%v", v))
+                jv, err := json.Marshal(v)
+                if err != nil {
+                        fmt.Fprintln(os.Stderr, err)
+                        return 1
+                }
+                annotate("SET_BUILD_PROPERTY", k, string(jv))
         }
 
         recipeExitCode, err := c.run(app.Context)
         annotate("STEP_CURSOR", BootstrapStepName)
         if err != nil {
                 if err != context.Canceled {
                         fmt.Fprintln(os.Stderr, err)
                 }
                 return -1
         }
@@ skipping 20 matching lines @@
                         err = fmt.Errorf("could not parse JSON from file %s\n%s\n%s",
                                 propertiesFile, b, err)
                 }
         }
         return
 }
 
 func annotate(args ...string) {
         fmt.Printf("@@@%s@@@\n", strings.Join(args, "@"))
 }